Impulse switch



April 7, 1942 c. 1 DAVIDSON 2,278,918

IMPULSE SWITCH Filed May 1l, 1939 HA QR/5, /f/fch; F057 AAW/5 FOP THE FIRM A Tref/MKS.

Patented pr. 7, 1942 IMPULSE SWITCH Chester L. Davidson, Burbank, C'alif., assignor to Aviation Patents, Inc., Los Angeles, Calif., a corporation of California Application May 11., 1939, Serial No.273,004 In GreatBritain May 13,v 1938 4 Claims.

My invention relates :to circuit controlling devices in general with special reference'to quickacting switches, and is directed specifically to the construction of a switch for releasing momentary impulses of current in an electric circuit.

In the operation of some electrical devices and apparatus it is required that electric energy be applied intermittently as momentary impulses of current. Manually operable switches of conventional types may be employed for such purpose provided the desired energization intervals are not too brief and provided it is permissible that the intervals vary in duration. In some situations, however, it is requisite that the current impulses be nearly instantaneous requiringl switch action entirely too rapid for manual manipulation, and some situations require a degree of uniformity in the duration of the impulses that is impossible to achieve by a wholly manual procedure, n

The general object of my invention is to satisfy the need in various situations for a switch means that is manually controlled yet operates to release current impulses of exceedingly brief and/or uniform duration.- A further general object is to incorporate means in such a switch for adjusting the duration of the current impulses.

My invention is characterized by the conception of combining with a sensitive quick-acting switch means an actuating means therefor having an operating cycle that is manually initiated but is carried out automatically at a controlled rate. The quick-acting switch means is adapted to respond to the actuating means in the course of the automatic operating cycle and therefore is uninfluenced by the means that is manually manipulated to initiate the operating cycle. Further objects of my invention, then, are to provide such an actuating means and to operatively relate the actuating means to the quick-acting switch in a manner to produce current impulses of the required character, duration, and`uniformity.

The energy for the operating cycle of the actuating means may be derived from any suitable source and applied in any suitable manner in the various practices of my invention. In the preferred form of my device, however, I contemplate deriving the required energy from the manual initiation of the actuating means. More specifically, it is my object to provide manually operable means to store venergy and then torelease the energy to the switch-.actuating means for carrying out said operating cycle automatically in a predetermined manner unaffected by the human equation.

Another object in mind is to provide for minimum time spacing of the current `impulses by so arranging the actuating means that a'substantial portion of the operating cycle of the actuating means must be performed after one impulse to produce the succeeding impulse.

A further specific object is to provide adjustable means for controlling the rate at which the operating cycle is performedl `or for controlling the actuating effect of the operatingr cycle on the switch means whereby the duration of the current impulses may be controlled;

My invention may be employed in various fields and may be `adapted to various devices for '4 bodiment of my conception by way of illustra tion. This embodiment has been designed specically to operate as what may be `called an impulse generator in an electric control system foran adjustable pitch propeller.

The above and other objects and advantages of my invention will be apparent in thek course of my detailed description to follow.

In the drawing: f

Fig. 1 is a front view of a device that may be mounted on the instrument panel of an aircraft for controlling the pitch of the aircraft propeller;

Fig. 2 is a medial section of the device taken as indicated by the line 2-2 of Fig. 1; s

Fig. 3 is a transverse section taken as indicated by the line 3 3 of Fig. 2; and

Fig. 4 is a wiring diagram of the circuit associated with the control device of Figs. 1 to 3.

An understanding of the function served by the device of Figs. 1 to 3 may be approached by rst considering the wiring diagram of Fig. 4, in which is diagrammatically shown an outer electromagnet coil I0 and an inner electromagnet coil Il. These two coils are part of a propellerpitch control system in which mechanism carried by the propeller hub is retarded in its rotation in one manner for increase of pitch on the part of the propeller blades and is retarded in the opposite manner for decrease in the pitch of the blades. The retardation for increasing and decreasing pitch is effected through selected energization of the two coils I0 and Il, which energization brings coacting surfaces into frictional engagement. Because of the relatively high angular velocities at which propellers are operated, only exceedingly slight retardation of the pitch controlling mechanism carried by the propeller shaft is required for a substantial change in pitch, and any retardation eiect that is at all severe may endanger the mechanism. Various measures have been taken to avoid undue retardation in the operation oi the pitch control mechanism among which is the safeguard afforded by my invention of limiting -energization of the electromagnet coils IIJ and II to exceedingly brief periods.

'I'he purposes of the present embodiment of my invention are: first, to make it impossible for the person operating the pitch control system to prolong continuous retardation of the pitch control mechanism to any damaging extent; second, to deliver to the electromagnet coils exceedingly brief impulses of current, impulses too momentary in duration for any conventional hand-operated switch; third, to provide adjustable means for controlling the duration of the impulses thereby to control the pitch-changing eiect of the impulses; and, fourth, to deliver impulses of such uniform duration that the operator may depend upon each impulse having a predetermined pitch-changing eect.

Fig. 4 shows a battery I2, one pole of which is connected to a wire I3 leading to one terminal of the coil I0, and to a wire I4 leading to a terminal of the inner coil II. The other pole of the battery I2 is connected to three switches placed in series, the three being an impulse switch generally designated I5, a master switch I5, and a selection switch I'I. These three switches may be arranged in any sequence, but in the sequence shown a wire I3 connects the battery I2 with the impulse switch I5, a wire 2B connects the impulse switch with the master switch I6, and a wire 2I connects the master switch to a movable switch member 22 of the selection switch Il. In the selection switch I1 the switch member 22 is movable between a position cooperating with a contact 23 and an alternative position cooperating with a contact 24, the contact 23 being connected by a wire 25 with the second terminal of the coil I and the contact 24 being connected by a wire 26 with the second terminal of the coil I I. If the master switch switch I will release an impulse of current which will iiow through one or the other of the two coils Il) and II as determined by the disposition of the selection switch I'I.

The impulse switch I5 in this particular control system may be in the form of an instrument adapted to be placed within reach of the pilot. As shown in Figs. 1 to 3, the mechanism of the impulse switch I5 is, by preference, contained within a cylindrical housing 30 having ears 3|' to receive screws 32 by which the housing may be mounted on an instrument panel 33.

For the sake of compactness as well as for convenience, a replacable fuse 34 for the circuits along with the master switch I6 and the selection switch I'I may be mounted on a face plate 35 of the housing 33, Fig. 1 showing a manuallyoperable lever 36 for controlling the master switch, and a second manually-operable lever 37 for controlling the selection switch. The drawing shows a cable 33 for the circuit wires connected to the housing 33 by a suitable cable fitting 39l The preferred form of my invention incorporates a quicio-acting switch 40 of the type known I6 is closed, actuation of the to the art as a micro switch, but other types may be employed. This switch 40 need not be described in detail, since its construction is not a part of my invention and since its operation may be understood by referring to the McGall Patent No. 1,960,020, entitled Snap switch, patented May 22, 1934. A switch of this type is characterized by extremely rapid operation in closing and opening and, more important in the practice of my invention, may be closed and then opened in exceedingly close sequence. For example, the micro switch 40 used in the construction shown in the drawing is normally open, but snaps to aclosed position when a plunger 4I extending irom the switch is pressed inward to s given point and snaps open when the pressure on the plunger is relieved sufficiently to permit the plunger to move only .001 inch in the return direction.

To accomplish the required momentary closing of the switch 4I?, I propose to employ a mechanism in which movement is initiated manually but which thereafter proceeds automatically in a predetermined manner to exert actuating pressure on the plunger 4I for a time interval of momentary duration. While suitable operating cycles may be afforded by various mechanical and electrical combinations, I prefer to employ mechanism involving the use of iluid pressure. The drawing shows the micro switch 40 mounted on an inner frame or bracket 42 that is connected to the rear wall 43 of the housing by screws 44 and is connected to the face plate 35 by screws 45. The mechanical means for transmitting pressure to the plunger 4I of the micro switch 40 may take the form of a, lever 46 journaled in ears 41 that are provided by the inner frame 42. When the lever is swung to the left, as viewed in Fig. 2, it moves against the plunger 4I of the micro switch.

In the preferred form of my invention I actuate the plunger 4I of the micro switch by fluidpressure-responsive means which may be, for example, in the form of a piston 5I) floatingly A, mounted in a chamber 5I formed by a cylinder 52. The piston 50 may be of hollow construction with an aperture 53 in its outer wall 54 to receive the upper end of the lever 46, the end of the lever being formed into a hook 55 to engage the inner face of the wall 54. The cylinder 52, which is supported from the face plate 35 of the housing, is formed with tongues or flanges 56 on its inner end to limit the rearward movement of the piston 50 and is also formed with an inwardly directed annular bead 51. It will be noted that the piston 5B is exposed to atmospheric pressure from the rear and from the front is exposed to the pressure prevailing in the chamber 5I. The normal position of the piston is toward the rear end of the cylinder 52'and a pressure differential caused by reducing the pressure in the chamber 5I below atmospheric pressure will tend to force the piston forward to actuate the switch 40,

The present form of my invention contemplates the momentary rareflcation of the air in the chamber 5I in a controlled manner to cause momentary closing of the micro switch. To produce such rarecation, pump means is employed and to produce the rarecation in a controlled manner the pump is arranged to be actuated automatically through at least the portion of its operation that produces the rarecation.

The pump means may comprise simply a hollow plunger E0 in the forward end of the cylinder 52, the pump plunger having an operating stem 6I that extends forward through the face plate 35 of the-housing and carries a knob or push button 62. `The stern 6I has an axial bore 63 and a radial bore 64 providing for passage of atmospheric air into and out of the cylinder 52. The plunger 60`is urged toward its normal forward position shown in Fig. 2 by a helical spring 65 within the plunger that seats against a metal bushing 66, the` bushing in turn seating against the aforementioned. internal bead 51.

If the pump plunger 60 is moved inward by manual depression of the operating button 62, a quantity of air will be displaced from the interior of the cylinder, the displaced air moving outwardly through the passage provided by the bores 63 and 64 in the plunger stem 6 l, and at the same time energy will be stored in the spring 65 to cause the return or expansion movement of the plunger 60 whenever the button 62 is subsequently released by the operator. It is contemplated that the spring-actuated expansion movement of the plunger 60 will be completed with the necessary rapidity to cause whatever degree of rarefaction of the air in the cylinder 52 is required for the desired momentary actuation of the micro switch. The degree of rarefaction will depend upon the volumetric change represented by the pump plunger movement, the rapidity with which that movement is made, and the freedom with which air flows through the passage provided by the bores 63 and 64. The degree to which the air in the chamber 5I is rareed may be adjusted by varying any one of these three factors; for example, I may mount an adjustable needle valve 61 in the stem 6l to control the freedom with which air may pass into and out of the cylinder 52.

The operation of the device disclosed in the drawing may be readily understood from the foregoing description. In the course of aircraft flight, the master switch I6 is kept closed; in other words, the lever 36 is placed at the on position as indicated in Fig. l. If the pilot desires to increase the pitch angle of the propeller blades at any time, he makes sure that the lever 31 of the selection switch l1 is in the position shown in Fig. l so that any current released by the device will be sent through whichever of the two coils I and Il will retard the pitch-changing mechanism in the required manner. The operator then presses the button 62 inward to contract the pump means, the plunger 6D being moved inward to its limit. The operator thereupon releases the button 62 to permit the plunger 60 to be returned automatically by the spring 65.

If the device is properly adjusted the rarefaction of the air in the chamber I will increase with the return movement of the plunger 60 to such an extent that toward the end of such return movement the resultant pressure differential acting on the floating piston 50 will cause the floating piston to shift forward momentarily to draw the lever 46 against the operating plunger 4| of the micro switch. If the needle valve 61 is adjusted to delay the required drop in pressure in the chamber 5| until near the end of the springactuated plunger movement, the pressure will begin to rise in the chamber 5I immediately after the required degree of rarefaction is attained, with the result that the floating piston will begin its rearward movement without pause. The impulse of current through the micro switch is exceedingly brief in duration not only because the reciprocation of the iioating piston 50 is extremely brief but also because the micro switch does not close until near the end of the forward movement of the floating piston and then opens as soon vas the return movement of the floating piston is initiated.

While my broad concept of an impulse switch may be eiectively carried out by a pneumatic arrangement as herein described, it will be readily apparent to those skilled in the art that other arrangements may be provided for accomplishing the' required operating cycle and that various changes,modications, and substitutions may be made without departing fromthe essence of my invention. I specifically reserve the right to all such changes, modifications, and substitutions that properly come within the scope of my appended claims.

I claim as my invention:

1. Means of the character described for controlling a circuit, said means including: a normally open quick-acting switch in said circuit adapted to snap closed in response to applied pressure and to snap open upon reduction of that pressure; an air chamber normally under atmospheric pressure; means to apply momentary actuating pressure to said switch in response to momentary rarefaction of air in said chamber; pump means adapted for contracting and expanding movement, said pump means being connected with said chamber to rarefy the air therein on its expansion stroke, said pump means being manually contractable; and yielding means operatively connected with said pump means to store energy on the contraction of the pump and to deliver that energy to the pump to cause said expanding movement in a predetermined manner.

2.- Means of the character described for controlling a circuit, said means including: a normally open quick-acting switch in said circuit adapted to snap closed in response to applied pressure and to snap open upon reduction of that pressure; an air chamber normally under atmospheric pressure; means to apply momentary actuating pressure to said switch in response to momentary rarefaction of air in said chamber; pump means adapted for contracting and expanding movement, said pump means being connected with said chamber to rarefy the air therein on its expansion stroke, said pump means being manually contractable; yielding means operatively connected with said pump means to store energy on the contraction of the pump and to deliver that energy to the pump to cause said expanding movement in a predetermined manner; and valve means to control the degree to which the air in said chamber is rarefied by said expanding movement.

3. Means of the character described for controlling a circuit, said means including: a switch in said circuit movable between an open position and a closed position, said switch being adapted to seek one of said positions as its normal position; switch-actuating means adapted to move through an operating cycle and in the course of said cycle to move said switch from said normal switch position to the other of said two switch positions for the duration of a time interval; yielding means; a chamber confining an air body, said chamber having a relatively small port to the atmosphere; and an initial operating means movable independently of said switchactuating means from a first position to a second position against the resistance of said yielding means to store energy in the yielding means, said yielding means being adapted to return said initial operating means from said second position 4. Means of the, character described for controlling a circuit as set forth in claim 3 in which said vent in said chamber is controlled by an adjustable means whereby the expansion of said air body caused by movement of said initial operating means from said second position to said rst position may be varied to vary the response to said switch-actuating means and thereby vary the duration of the interval during which said 1o switch is held out of said normal switch position.

CHESTER L. DAVIDSON. 

